If you find that you are still getting charged regularly for data even if you have turned off your mobile data on your phone, please ensure that your location services is turned off.

If you are using an Android phone, please go to Settings ->Location and disable this function. Also check if the location mode is set to GPS only.

If you have an iPhone / iPad, please go to Settings -> Privacy -> Location Services and turn Location Services off. Also ensure that your apps do not update by going to Settings -> General -> Background App Refresh and turn the setting to Off to turn if off for all apps.

By doing this, the phone will no longer constantly check your location or ping nearby cell towers.